The described invention relates in general to welding systems and devices, and more specifically to an arc welding system that includes tandem welding torches for use in narrow-groove applications. Gas metal arc welding (GMAW), sometimes referred to by its subtypes metal inert gas (MIG) welding or metal active gas (MAG) welding, is a semi-automatic or automatic arc welding process in which a continuous and consumable wire electrode and a shielding gas are fed through a welding apparatus. GMAW produces high-quality welds and yields high productivity in many applications. In GMAW, the welding heat source is an arc maintained between the consumable wire electrode and the workpiece. The weld is formed by melting and solidification of the joint edges together with filler material transferred from the electrode. The positive (+) lead is connected to the torch and the negative (−) lead is connected to the work piece for providing a relatively consistent voltage to the arc. Arc voltage is the voltage between the end of the wire and the work piece. The purpose of shielding gas is to protect the weld area from the contaminants in the atmosphere and the gas can be inert, reactive, or mixtures of both. Argon, helium, and carbon dioxide are the main three gases used in GMAW. GMAW process variables include welding current (electrode melting rate), polarity, arc voltage (length), travel speed, electrode extension, electrode size, and shielding gas composition.
Many manufacturers of thick-section components such as pressure vessels, heavy equipment, ship hulls, thick-wall pipe, and the like join parts together using high-deposition-rate welding processes such as GMAW and/or Submerged Arc Welding (SAW) with conventional open-groove designs. Although these processes may be considered to be high-deposition-rate processes, they are not necessarily high-productivity processes for this application due to the large number of welds that are required to fill conventional open-groove weld joints. Other manufacturers of these components join parts by using low-deposition-rate welding processes such as gas tungsten arc welding (GTAW) with narrow-groove designs. Although the narrow-groove design drastically reduces overall volume of the weld joint, the lower deposition-rate processes used with these joint configurations prevent them from being high productivity processes. As the market for these components continuously drives the need to reduce cost while maintaining a high level of quality, innovative methods of joining these components together at much higher productivity levels must be created.